The invention relates to the field of homogenizing units.
A homogenization process is used to reduce the size of the drops in an emulsion or the particles in a suspension and make them as homogeneous or equal to each other as possible. The homogenization process generally comprises the passage (forcing or blow-by) of a liquid to be homogenized through a nozzle or a very fine opening or gap, under a suitable pressure, in order to cause impacts and breaking down of the particles; in addition the flow of particles leaving said passage at high speed is caused to hit a so-called impact ring, which further contributes to reducing particle size and improving homogenization.
Homogenizer units currently in use comprise a homogenizing valve downstream of a compression head whose function is to pump liquid to be homogenized at high pressure; said liquid is introduced, generally axially, through said valve into a pressure chamber defined by an impact head, which is pressed with adjustable force towards an opposite surface of an annular passage head, which is fixed in the valve body. Such a homogenizing valve according the state of the art is shown schematically in axial sectional view in FIG. 1. In this figure, reference number 1 indicates a high pressure chamber in lower valve body 2 into which the liquid to be homogenized is introduced in the direction of the arrow F1 at high pressure up to over 1000 bar; the high pressure chamber has a diameter D1. Said lower valve body 2 houses a passage head 3 with which an impact head 4 cooperates pressed with adjustable force by guiding and pressing shaft 5. The impact head is guided by fixed radial wings 6 integral with upper valve body 7. The product at high pressure which is forced to pass through a radial passage gap (height h1) between the impact head 4 and the passage head 3 loses pressure and gains velocity, and hits at high speed against impact ring 8, said ring being housed in the upper valve body 7 and facing the radial passage gap. The homogenized liquid passes along the radial wings 6 into a low pressure chamber 9 and flows out in the direction of arrow F2.
This arrangement is widely used. However, in the radial passage gap between the impact head and the passage head, the velocity of the fluid is not evenly distributed across the height of the passage gap and this results in differences in homogenization in the various layers of fluid. In addition, turbulence and cavitation occur, these phenomena increasing with the height of the gap. On the other hand, if the height of the gap were reduced, which could be advantageous for improving the particle size distribution of the product to be processed, with the same flow and homogenization pressure applied, it would be necessary to construct a valve with a larger diameter D1 (FIG. 1) and this would involve having to apply a considerably greater force to the impact head to obtain the same homogenization pressure. This would therefore result in a greater mechanical complexity of the equipment, the presence of a high pressure hydraulic control system and consequently higher costs.